ITR/SI: Wireless Transmission Optimization for Bursty Data Traffic

在提供无缝的信息“超级高速公路”方面，无线信道预计将发挥与有线互联网一样的主导作用。 未来，无线数据流量将越来越多地由各种多媒体主导，如实时视频、电子邮件、Web下载，而不是语音传输。 信息技术研究计划所设想的“无系绳通信和网络”需要深入研究如何处理无线信道上的多媒体传输。 各种多媒体具有与语音非常不同的业务特性，其特征在于不同的延迟约束和突发性。处理突发数据主要在网络通信中解决。 社区集中在流量延迟约束，丢包率（假设是丢包率），和信道容量之间的关系，捕获的措施，如“有效带宽”。有线（光纤、铜缆等）中的网络问题 通过这种方法，已经成功地解决了媒体的问题，因为这种信道本身就是低误差信道。 然而，网络社区基本上忽略了这样一个事实，即存在一个非常真实的、非理想的物理信道来承载这些数据。 因此，这些方法向无线介质的迁移遇到了一个重大障碍-无线信道本质上是一个非常嘈杂、非鲁棒的信道。 因此，对于无线信道，重要的是要考虑突发性和信道差错两者对分组丢失的影响。 研究人员一直在以（PI认为）特别的方式考虑这两种影响。 本提案旨在以系统和逻辑的方式处理这一问题。 具体而言，PI建议引入突发性和信道条件的联合测量，并使用该测量来解决在无线系统的竞争用户之间分配稀缺资源的关键问题。 拟议的联合方法是一个根本性的变化，在范式，因为它试图综合的想法，从网络和通信理论社区。 源突发以及信道错误（由于噪声、衰落等）影响信道容量的标准概念是由于数据通信中有限延迟的要求。 因此，PI制定了一套与延迟和数据包丢失相关的初始措施（详细信息见完整提案）。 该措施是基于随机编码误差指数的方法，在信息理论的设置。 为了降低丢包概率，无线发射机必须以尽可能高的数据速率进行传输。 但是，由于传输错误，高传输速率将意味着无线信道上的高分组错误概率。 PI开发的措施试图捕捉这种权衡。 初步分析表明，使用这种措施确实提供了一个很大的好处（在设计一个最佳的系统）突发业务传输衰落的无线信道。 目前研究的第一步将是完善已制定的联合措施。 这将涉及使用更复杂的源业务模型，更复杂的衰落信道模型，和实际的信道编码方案。 所开发的措施，然后将被用来设计最佳的或强大的计划（如有需要），以分配无线资源的竞争流的数据流量。 这将涉及开发调度流量控制算法，以及相关的自适应信道编码方案，使用联合措施。 总之，这项研究将介绍一个全新的模式，在无线信道上的突发数据流量的传输优化，然后在实际情况下证明新的范式的实用性。

The wireless channel is expected to play as dominant a role as the wired internet, in providing seamless information 'super-highway'. In the future, wireless data traffic will be increasingly dominated by a variety of multimedia, such as real-time video, email, web downloads, as opposed to voice transmission. "Tether-free communication and networking', as envisioned by the Information Technology Research program, requires intensive research into handling the transmission of multimedia over the wireless channel. Various multimedia have very different traffic characteristics than voice, being characterized by different delay constraints and burstiness. Handling bursty data has been addressed primarily in the networking communit. The community has focussed on the relationship among the traffic delay constraint, the packet loss rate (which is assumed to be the packet drop rate), and the channel capacity, captured by measures such as "Effective bandwidth'. Networking problems in wired (fiber, copper, etc.) media have been successfully solved by this approach, because this channel is inherently a low-error channel. However, the networking community has by and large ignored the fact that there is a very real, non-idea physical channel on which this data is carried. Therefore, the migration of these approaches to the wireless medium meets a significant obstacle- the fact that the wireless channel is inherently a very noisy, non-robust channel. Thus for wireless channels, it is important to consider the effect on packet loss of both, burstiness and channel errors. Researchers have been approaching the issue of considering both these effects in (the PI believes) an ad hoc manner. This proposal intends to approach the issue in a systematic and logical manner. Specifically, the PI proposes to introduce a joint measure of burstiness and channel condition, and use the measure to solve the key problem of allocating scarce resources among competing users of a wireless system. The proposed joint approach is a fundamental change in paradigm, since it attempts to synthesize ideas from the Networking and Communication Theory communities. The reason why source burstiness as well as channel errors (due to noise, fading, etc.) affect the standard notions of channel capacity, is due to the requirement of finite delay in the data communication. The PI has therefore developed an initial set of measures (details in the full proposal) that relate the delay and packet loss. The measure is based on the random coding error exponent approach, developed in an information theoretic setting. To reduce the packet drop probability, the wireless transmitter must transmit at as high a data rate as possible. But a high rate of transmission would imply a high packet error probability on the wireless channel, due to transmission errors. The measure developed by the PI attempts to capture this trade-off. Preliminary analysis indicates that using this measure indeed offers a substantial benefit (in terms of designing an optimum system) for bursty traffic transmission over fading wireless channels. The first step in the current research would be to refine the developed joint measure. This would involve using more sophisticated source traffic models, more sophisticated fading channel models, and practical channel coding schemes. The developed measure will then be used to design optimal or robust schemes (as the need may be) to allocate wireless resources to competing streams of data traffic. This will involve developing scheduling flow control algorithms, and the associated adaptive channel coding schemes, using the joint measure. In summary, this research will introduce a fundamentally new paradigm for transmission optimization of bursty data traffic over wireless channels, and then demonstrate the usefulness of the new paradigm in practical situations.